Double stroke cylinder



Sept. 30, 1969 p, w, ADLER ETAL 3,469,503

DOUBLE STROKE CYLINDER Filed Oct. 16, 1967 O 4 2 ll 6 2 B. 8 2 m 2 1 8 2 2 3 I 4 8 3 3A 8 v72 3 9 a 6 3 6 3 on 2 2 Q 4 m M. 4

Jr. A. PAULS A TTORNE Y United States Patent US. Cl. 92-62 2 Claims ABSTRACT OF THE DISCLOSURE A fluid-operated cylinder construction having a floating piston positioned so as to accurately stop the travel of a piston rod in a predetermined intermediate position between a fully extended and fully retracted position.

Background of the invention In the past, it has been customary to utilize a single stroke cylinder for operating valves, positioning apparatus, etc., wherein the piston rod travels under pneumatic or hydraulic pressure between a fully extended and a fully retracted position, as limited by the piston in the cylinder housing. If an additional stop or shorter stroke were required in the operation, it necessitated the utilization of an additional piston and cylinder having the correct length. Although it was possible to modify the length of the stroke of the rod within the cylinder, through the use of stopping lugs, nuts, and bushings, it was not possible to provide an accurate intermediate stop between the fully extended and fully retracted position.

Summary of the invention The present invention is directed to a novel cylinder structure having a floating piston which provides a positive intermediate stop for the piston rod between the extremities of its stroke. It is now possible to eliminate the need for an additional piston and cylinder where a threeposition stop is required, since the length of the cylinder within which the piston rod travels will determine the fully extended and fully retracted position of the rod, whereas the floating piston can be designed to provide an intermediate stop at virtually any desired location between such extremities.

It thus has been an object of the present invention to devise an improve cylinder structure which obviates the problems heretofore encountered in the art and provides means for accurately stopping the travel of the piston rod in a predetermined intermediate position between the extremities of its stroke.

Brief description of the drawing The figure is a cross-sectional view of a preferred embodiment of the invention.

Description of the preferred embodiment Referring to the figure, improved cylinder apparatus 10, embodying the present invention, includes a stepped cylinder housing 12, closed at its opposite ends by .a pair of end caps or plates 14, 16, which are secured in position by means of tie rods 18 and nuts 20. Although the customary sealing gaskets 22 are shown between the cylinder 12 and it end plates 14, 16, it will be appreciated that the apparatus could be formed unitarily, such as by welding.

The cylinder housing 12 is provided with a shoulder or stepped portion 24 which forms a chamber 26 at one end and a smaller chamber 28 at the opposite end. A floating piston 30 is positioned for sliding movement within chamber 26 between end cap 14 and shoulder 24. The floating piston 30 has a cylindrical extension 32 which is slidable longitudinally within smaller chamber 28. A piston rod 34 extends through end cap 14 and floating piston 30, and has an integrally formed piston 36 positioned for sliding movement within cylindrical extension 32. Suitable 0 rings or gaskets 38 provide seals for the various movable parts within the chambers. A snap ring 39 is retained adjacent the bottom of the cylindrical extension 32 so as to limit the downward movement of plunger 36 within cylindrical extension 32, and transmit such movement to the floating piston 30, limited however to the stop or shoulder portion 24.

A port 40 extends through end cap 14 and communicates with chamber 26. In a like manner a port 42 extends through end cap 16 and communicates with chamber 28. An additional port 44 is formed in the shoulder or step portion of the cylinder housing 12 and communicates through an opening 46 formed in the wall of the cylindrical extension 32 with the interior of cylindrical extension 32 above piston 36, when the floating piston 30 is in its retracted position. An exhaust or drain line 48 maintains atmospheric pressure within the chamber 26 behind the shoulder portion of floating piston 30.

When port 40 is pressurized, the cylinder apparatus 10 functions as a normal single stroke cylinder, with the stroke limited to that of piston 36 within cylindrical extension 32. That is, the area of floating piston 30 exposed to the pressure applied through port 40 is greater than that area exposed to pressure through port 42, and accordingly the floating piston 30 will remain stationary against shoulder 24 when port 40 is pressurized, and will function as the end cap for the travel of smaller piston 36.

With port 40 pressurized, the piston 36 is moved to its outward position within cylindrical extension 32 by pressurizing port 42 and exhausting port 44. Accordingly, piston 36 will move to its extended position within cylindrical extension 32 and abut against the inner surface of floating piston 30. However, due to the fact that a greater area of floating piston 30 is exposed to the pressure applied from inlet port 40 than is exposed to the pressure applied to inlet port 42, the floating piston will remain stationary against shoulder 24 and function as a set intermediate positioning stop for piston rod 34 when both ports 40 and 42 are pressurized.

The fully retracted position of the cylindrical apparatus 10 is accomplished by maintaining port 40 pressurized, exhausting port 42 to the atmosphere, and pressurizing port 44, which retracts piston 36 within the cylindrical extension 32, as limited by snap ring 39. When retracting the piston 36 within cylindrical extension 32, there is no tendency to unseat the floating piston 30 from shoulder 24, since the port 42 is open to the atmosphere and the pressure applied to port 44 is exerted equally against the bottom portion of floating piston 30 and the top portion of piston 36 so as to ultimately equalize the pressure exerted on the floating piston 30 by port 44. However under such conditions, pressure from port 40 retains the piston 30 in engagement with the shoulder stop 24.

The fully extended position of the cylindrical apparatus 10 is obtained by exhausting both ports 40 and 44, and pressurizing port 42. Under these conditions piston 36 is moved toward its extended position within cylindrical extension 32 and engages the under surface of floating piston 30 pushing it outwardly until the floating piston contacts the inner surface of end cap or plate 14. If desired, the system can then be returned to the intermediate position merely by pressurizing port 40, which due to the differential in area will retract floating piston 30, having piston 36 in engagement therewith, to its intermediate p0- sition in contact with stop 24. Piston 36 will remain in engagement with the lower surface of floating piston 30 during this retraction, due to the fact that port 42 is still pressurized, thus returning piston rod 34 to a preset intermediate position.

If desired, the system may be retracted from the fully extended position to the fully retracted position by pressurizing port 40 and port 44 while exhausting port 42 to the atmosphere. Under these conditions the floating piston 30 is first returned to its retracted position against stop 24, and piston 36 is retracted within cylindrical extension 32 to the extent of snap ring 39. It will be observed, that exhaust or drain line 48 is always open to the atmosphere so that unwanted pressures and vacuums are avoided in chamber 26 behind floating piston 30.

Although we have disclosed the now preferred embodiment of the invention it will be apparent that various changes and modifications may be made thereto Without departing from the spirit and scope thereof.

We claim:

1. An improved fluid-operated piston and cylinder apparatus for providing an extended, a retracted, and a predetermined intermediate piston rod position which comprises: a cylindrical housing having closed end portions; a stepped portion formed intermediate the ends of said housing providing a first chamber at one end of said housing and a second chamber of reduced cross section at the opposite end of said housing; a floating piston positioned for movement within said first chamber having a cylindrical extension slidable within said second chamber; a piston rod extending through a closed end portion of said housing and said floating piston; means sealing said first chamber from said second chamber; a piston connected to said rod and slidably movable within said cylindrical extension; a shoulder stop formed by said stepped portion for determining the retracted position of said floating piston; an inner end portion of said first chamber behind said floating piston having port means only in communication with the atmosphere; port means in communication with an outer end portion of said second chamber for providing the sole pressure means to move both said piston and said floating piston to their extended positions; port means communicating with an outer end portion of said first chamber forwardly of said floating piston for both moving said floating piston to its retracted position, and when in such position for maintaining an intermediate position stop for said piston rod; and port means communicating with the interior of said cylindrical extension, only when said floating piston is in its retracted position, for moving said piston and its associated piston rod to their retracted position.

2. Piston and cylinder apparatus as defined in claim 1 wherein an outer end portion of said cylindrical extension is in open communication with both said second chamber and said first-mentioned port means.

References Cited UNITED STATES PATENTS 2,510,314- 6/1950 Jirsa 9262 X 2,649,842 8/1953 Caldwell et al. 92-6-2 X 3,150,563 9/1964 Carrigan et al. 9262 X 3,158,070 11/1964 Olson 92-62 X 3,208,354 9/ 1965 Topinka 9262 X 3,312,146 4/1967 Quere et a1. 9262 X FOREIGN PATENTS 999,277 10/ 1951 France. 888,036 1/ 1962 Great Britain.

911,709 11/1962 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner IRWIN C. COHEN, Assistant Examiner US. Cl. X.R. 92-65 

